I read an article in the Times about elderly people who are living there now. They say the whole thing has been exaggerated by the media and it's perfectly safe. Of course there's some places where they can't go... I don't really understand how they get their food delivered.. anybody got a link to the people I'm talking about? They were definitely inside the Chernobyl dead zone, but whether they were in the town itself or another nearby town which had been evacuated I can't remember.

I am not too informed about the radiation levels and how they work, but I have some curiosity about how this compares to the spots where the A-bombs where dropped in Japan during WWII. Are those areas populated again? If so, how long did it take for them to be habitable again? Or is this a whole different level of radiation and thus incomparable?

I spoke with a bio professor about this a few years ago before I went on a trip to the Ukraine to do the "canned" Prypiat/Chornobyl tour. The abundance of wildlife is misleading. Since there is no human competition, there is going to be a lot more wildlife. But much of it has a higher mortality rate and isn't without its share of defects.

He mentioned that for humans to live there, we're probably easily looking at 100-500 years before the radiation is at acceptable levels. Once the wildlife have fewer problems (e.g. thryroid disorders), it may be safer for humans to move in. A good experiment would be to take a sampling of various types of wildlife--perhaps the ones most sensitive to certain radiation effects--and record the data on a yearly basis. Once the animals stop succumbing to radiation effects, it might be safe to move in, but you're going to have to consider other problems such as plant sequestration of radioactive isotopes. That birch may burn really well in the wintertime, but how much I-131 has it taken in (just a hypothetical statement)?

There is a difference between the study in this story, and the previously reported (this is my understanding). The previous stories seem to count the number of wildlife now and compare them to what was there before the accident. It is not surprising that without people, the number of animals and creatures will increase.

This study compares the number of animals to the number that would be present in a similarly uninhabited, uncontaminated zone. It appears that there are fewer than would be expected in a non-contaminated zone. There are accounts of pigeons with tumors and such.

These findings are not surprising, but it's good to know what's going on.

I can only assume that the PR/morale implications of driving away a few grandparently types, who are going to die soonish anyway, at bayonet point just wasn't worth it(and/or they had their hands full with more important things, like making sure that opportunistic looters weren't exporting cesium and strontium coated parts and food items to every grey and black market in the area...).

I've seen estimates from 200-10000 years depending on how close you are from the reactor.

What I don't understand, is why isn't this area used to build more nuclear reactors? It's not like there's anyone there to scream NIMBY, or that it'll be a bigger disaster if another reactor goes boom, which shouldn't happen if they use a modern reactor design. The only issue I see is employee safety, and that could be virtually eliminated given a reactor that is designed to shield the workers from the outside excess radiation.

It would be interesting to do followup studies of these people, especially to establish their natural resistance/tolerance to those radiation levels. Imagine the long-term prospects of a group of highly-tolerant individuals - do they have highly-effective repair mechanisms, highly-effective elimination systems, or what else?

This study compares the number of animals to the number that would be present in a similarly uninhabited, uncontaminated zone.

Actually, this study counts the number of species, not the number of animals; in their words the exclusion zone shows a "reduced biodiversity". So what the study really shows is that some species are holding up better in this environment than other species. Darwin would approve.

131I has a half life of 8 days. Basically all 131I released from something like Chernobyl is as a direct fission product of 235U.

Within a few months, substantially all the 131I is gone.

The "worst" things released for habitability, then, are the things with intermediate half-lives of a few years. The worst of these is the ~100 gigabecquerels of 125Sb released, and the 500-600 gigabecquerels of relatively short-lived isotopes of Cesium.

At this point, open-air dose rates and ground dose rates are about 1/100th of the first day dose; further gains are going to be slower because longer-lived isotopes dominate, but will be another factor of 20 in the next twenty years. Viewed another way, someone who spends their whole 75 year life in the present exclusion zone starting twenty years from now will receive a lower dose than someone who experienced the first ten days after the accident, and very few of those people died. (And there's considerable evidence that acute, high doses are much more dangerous than an equivalent dose delivered over a long time).

(According to UN reports, less than 50 deaths; most of which were emergency workers, but included 9 children who died from thyroid cancer from 131I).

Or is this a whole different level of radiation and thus incomparable?

WWII A-bombs released a few kg of fission products at high altitude. Chernobyl had tons of the stuff at ground level. A more direct comparison would be the ground level thermonuclear tests the US did on Pacific Ocean atolls. These also released fission products measurable in tons. (Most fusion bombs use the fusion mainly as a neutron generator and actually get the majority of their yield from fission of cheap U238.) Parts of those atolls are still uninhabitable.

It's an interesting comparison you offer, but I'm not sure what conclusion should be drawn as to safety. Half life for the Antimony (125Sb) would be 1008 days, so at 30 years out, we are looking at about 1/16th of the contribution you are projecting for 20 years. The numbers you use suggest human return certainly ought to be possible within 30 years, if not 20, even erring on the side of extreme caution.
But, I doubt there is a single mammalian species in the area that has half as long a typical time to reproductive maturity as humans. If a species such as deer or wild dogs is showing declining reproduction when they mature in as little as a single year, humans simply have to be more vulnerable to the same effects due to what's called reproductive differential. It's not really necessary to understand the effects that are causing the population decline in detail, or have a clear stepwise model of all the mechanisms involved, to predict this.* So, my estimate would be to wait until the fast reproducing species are all acting stable, and then wait another couple or three half lives of the Antimony, even if this takes more than 30 years total.

*assuming the species isn't declining because of being hunted to excess by humans or because we have screwed up the broader environment - rather that it's declining because of something originating with the Chernobyl event - we do still need to make sure of that!

Not that you're interested in my left nut, but I'd give my left nut for pictures of these things. Any of the relevant articles have anything more than the footnote in the paper you cited? (I can't seem to find the original, but that may be because it's not available online, only in dead-tree form, and the library's not open 24/7.)

Hey now, there's no problem with sans serif fonts when used as "headers" and advertising text. It's using the blasted things for "body" text that's evil. I think we're stck with it for a while, thanks to all the amateur graphics designers that came of age during the time of really low DPI screens. One day maybe web "designers" will rediscover the difference between readability and mere legibility, and sans serif body fonts can rest next to Geocities in the graveyard of early computing history.